Thought I'd create a page to post my findings while developing an FBML interface to a web app being ported to Wicket. Feel free to hop in & contribute.
Strip wicket tags from markup while in development mode
Facebook ignores any wicket tags (such as <wicket:panel> etc) in your FBML markup, which of course makes a page using them non-functional. Running your application in deployment mode causes the wicket tags getting stripped, but disables a lot of other useful debug features as well.
To strip the wicket tags from your markup while running in development mode, add the following to your application's init():
getMarkupSettings().setStripWicketTags(true);
Thanks to Gerolf Seitz, Uwe Schäfer and Larry Zappaterrini on the wicket users who all answered my question in no time.